Strike-Interpretive Gridding, SI-GRID, is a new software tool that provides the geoscientist with a specialized, simple, interactive software program for the express purpose of building very high definition, coherent grids, from profile data. It is an efficient, easy to use routine that provides immediate confirmation of results, visually.

Profile Data:

A geophysical map begins with detailed information along airborne or ground profiles. Approximately 80% of the map is blank; unknown values to be predicted. How the blank space is filled determines the quality of the final map. The basic rules for interpolation are:

+ A smooth transition from line to line
+ No modification of the profile data

Trend Enhanced Bi-Cubic Spline:

This interpolation method meets the basic interpolation requirements. Its limitation is that a single trend direction must be applied to the entire map. In this example SW/NE trends are reasonably presented but NW/SE trends are broken and distorted.

Minimum Curvature:

This interpolation method can meet the basic interpolation requirements, but can also be relaxed about the degree of fit to the profile data and thus smooth the result. Trend emphasis tends to be towards the closest points, which are perpendicular to the line direction. In this example, a uniform but mediocre redition of NW/SE and NE/SW trends results.

SI-Grid:

This interpolation method meets all the basic interpolation requirements. Note how well the presentation renders anomaly detail for both NW/SE and NE/SW trend directions simultaneously.

SI-GRID is a computer gridding process that automatically identifies and protects trends that may continuously vary throughout a map. No longer does one trend direction need to be favoured at the expense of another. The process builds the interpolated data set entirely from the originating profile data and does not employ any smoothing or filtering steps to artificially improve the apparent coherence of the data. The new SI-GRID process can significantly improve the quality of the basic gridded data and all of the interpretive analysis tools that build upon it.

The example above, from Northern Ontario, is an excellent illustration of a geological scenario that is impossible for conventional gridding routines to properly depict. At the left is the typical presentation of a string of circles along strike. By altering grid orientations, one axis could be enhanced but with added discontinuity to the other. The SI-GRID process is able to optimize both axes simultaneously and provides an excellent rendition of each linear feature. Anomaly width and cross sectional detail are clearly presented in map form for proper consideration by the interpreter.

If you have a dataset in which the geological complexity appears to exceed the flight line density and interpolation quality; contact Scott Hogg & Associates Ltd. for a quotation on the SI-GRID process.